If you still haven't figured it out, it is a bone from most likely a deer carcass, most likely a front leg and from the joint there are 2 bones that have created a hook that is lapped over the top of the dog blanket under her neck. Whether she was rolling on the carcass or the bone, it was most likely the way it got bound on the blanket.
Kenya was ultimately asked to drop her prize. With much chagrin, she relented, Marty grabbed her collar and I tossed her token into a field with a good fence so that she could not return to the scene of the capture. Whether it's old age or a predator, these carcasses are not rare and a dog on the loose is always attracted to the parts that remain.